Can you confirm the only connection the headset has is a USB connector and not any 3.5mm headphone jacks? Through 3.5mm jacks hissing / whining / crackling is common for lower-end components but to affect a USB-connected headset? That's some seriously noisy power flowing through / around your computer.

__________________"The computer programmer says they should drive the car around the block and see if the tire fixes itself." [src]